As you saw in the previous section, activating change tracking also activates workbook sharing, the Excel feature that enables two or more users to collaborate on a workbook at the same time. This is a powerful tool because it enables you to share the burden of building a workbook.

For example, if you coordinate a budget model, you might want to share the workbook and assign a different worksheet to a user in each department. I should point out here that although turning on change tracking also turns on workbook sharing, the opposite is not the case. That is, you can share a workbook without also tracking changes. Follow these steps to share a workbook:

1. If another person is currently using the workbook, ask that person to close the file.
2. Choose Review, Share Workbook. Excel displays the Share Workbook dialog box.
3. Activate the Allow Changes by More Than One User at the Same Time check box.
4. Click OK. Excel tells you it will save the workbook.
5. Click OK.

Excel displays [Shared] in the document title bar to remind you that the workbook is shared. You and your collaborators are now free to work on the file at the same time. Note, however, that Excel doesn’t allow the following operations while a workbook is shared:

• Inserting and deleting ranges (although you can insert and delete entire rows and columns)
• Merging cells
• Creating lists
• Creating or modifying PivotTables
• Deleting or moving worksheets
• Applying conditional formatting
• Working with scenarios
• Subtotaling, validating, grouping, and outlining data
• Inserting charts, symbols, pictures, diagrams, objects, and hyperlinks
• Checking for formula errors

To ensure that you always work with the most up-to-date version of the file, save the workbook. This tells Excel to display other reviewers’ changes in your view of the workbook. If any changes are added, Excel displays a dialog box to let you know. To control when Excel updates a shared workbook, follow these steps:

1. Choose Review, Share Workbook to display the Share Workbook dialog box.
2. Click the Advanced tab.
3. In the Update Changes group, click one of the following options:
   • When File Is Saved—When you activate this option, Excel updates the workbook automatically when you save the file.
   • Automatically Every X Minutes—When you activate this option, Excel updates the workbook using the interval you specify (the minimum is 5 minutes; the maximum is 1,440 minutes). You can also elect to have Excel save your changes at the same time or just see the changes made by other users.
4. Click OK.

If you want to know who is currently using the workbook besides yourself, choose Review, Share Workbook. As you can see in Figure 6.4, the Who Has This Workbook Open Now list displays all the current users. If you want to prevent a reviewer from using the workbook, click the user and then click Remove User. Note, however, that you should use this technique only as a last resort because it can easily cause the user to lose unsaved changes.

It’s safer (and friendlier) to ask the person directly to save his changes and close the workbook.

What happens if another user changes a cell, saves his changes, and then you change the same cell before updating? This creates a conflict in the workbook versions that must be resolved. To do this, Excel displays the Resolve Conflicts dialog box, shown in Figure 6.5. You have two choices: Click Accept Mine to accept your change or click Accept Other to accept the other user’s change.

To control how Excel handles conflicts, follow these steps:

1. Choose Review, Share Workbook to display the Share Workbook dialog box.
2. Click the Advanced tab.
3. In the Conflicting Changes Between Users group, click one of the following options:
   • Ask Me Which Changes Win—When you activate this option, Excel displays the Resolve Conflicts dialog box.
   • The Changes Being Saved Win—When you activate this option, Excel automatically accepts your changes.
4. Click OK.